Yes they all do contain aluminum - but the percentage varies widely. This is one of the reasons you want a well sourced Bentonite that states it is for internal cosumption.

Healthfood stores tell you that whatever clay they have works internally even if it doesn't say so on the label. It's too expensive for the company to make the claim, blah blah blah. (this happened to me in 2 different stores locally)

Maybe so, but because of potentially high aluminum content and other factors I'll stick with the stuff rated for internal use.

I seem to remember that the sodium bentonites (used more for industrial app) tended to have higher aluminum content than the calcium bentonite.

The clay does such a good job or retaining metals that it's nothing to worry about except in the case of very high concentrations. Again, make sure it's sold for internal consumption.